Wednesday, April 16, 2014

Stream food webs in an altered environment

The following is guest post by Briana Cairco, a freshman at Clemson University enrolled in Dr. Barrett's Creative Inquiry course focused on amphibian conservation.

My name is Briana Cairco, I’m a freshman wildlife and
fisheries major and entomology minor at Clemson University in South Carolina.
This semester I’ve have the wonderful opportunity to take a Creative Inquiry
class studying the effects of exurbanization on salamanders in Appalachia. As
you may or may not know, the Appalachian Mountains are home to more species of
salamander than any other place on earth, so there is no better place to study
salamanders than in our own backyard.

So, what is exurbanization? Exurbanization is basically
urban sprawl, people like having the amenities of the city, but want to live in
a more rural area. So, land outside of cities is developed to provide easy
access to the city, and a more natural environment to live in. This process may
be the best of both worlds for humans, but these exurban communities can
decimate the ecosystem they’re in. These communities may not seem so bad at
first glance, but when you consider the sedimentation from the construction,
the runoff from fertilized lawns, the increased salinity from road salt, and so
many other factors that impact the streams, the threat these communities pose
to amphibians is very real. Our goal this semester is to sample streams with a
varying exposure to these developments in order to determine the effects
exurbanization has on the salamander population as a whole.

Within our group each person is conducting his or her own
research on a related topic. I chose to research the relationships between
species of macroinvertebrates and species of salamanders. I will be using the
salamander data we get and collecting data on the variety of invertebrates and
looking at any correlation between the two. Salamanders are the top predator in
these streams that we are examining, so when their populations suffer it is
safe to assume that the invertebrate community will change as well. Either they
will increase because they aren't being hunted, or they will decrease because
whatever is threatening the salamanders is threatening them too.

Certain species of both invertebrates and salamanders are
more sensitive to environmental changes. When we look at the data between sites
with different water quality readings it would be interesting to see if any of
the species seem to be sensitive to particular variables. Between sites with similar
water quality, results may show which invertebrate and salamander species have
interdependent relationships. There are so many variables in these sites that
it could be hard to say whether particular species have a special relationship,
but it would be really interesting if for example, sites with caddis fly larvae
as the predominant invertebrate also seemed to have the most black belly
salamanders. Maybe this study could show if the salamanders have a favorite
food, or it could just show which invertebrate and salamanders have similar
habitat preferences.

The task is a little daunting since there are so many things
out of our control, the invertebrate populations will be affected by the
season, so I will have to take into account the breeding period for the species
we find. Also, the size of invertebrate
is important a small stream could support thousands of tiny stonefly larvae,
but obviously not as many hellgrammites. So instead of just comparing the
numbers, I’ll need to compare changes in species abundance between sites.

I will be using this identification
key from Auburn University to identify the invertebrates by order, then by
their feeding group. There are four feeding
groups; shredders, which rely on dead plant and animal material,
scrapers/grazers, which eat living plant matter and algae, predators, which eat
other invertebrates, and collectors/filterers, which filter fine material from
the water. Most stone fly larvae are
shredders, except for families Perlidae, Chloroperlidae, and Perlodidae which
are predatory, and have obvious physical differences. The mayfly larvae we will
encounter will be collectors, except for family Heptageniidae which are
scrapers, and are also easy to differentiate because they appear to have no
head. The caddis fly larvae are more
difficult to differentiate so since the majority of species are scrapers, any
caddis fly larvae will be classified as a scraper. The megalopterans (like
hellgrammites) are predators; as are both dragonfly and damsel fly larvae. I
think these feeding groups will be helpful in connecting stream quality and
both salamander and invertebrate abundance.

I’m really excited to start sampling, and I haven’t seen any
articles about the relationships between certain invertebrates and salamander
species yet, so I have no idea what to expect.